Position sensors have been increasing in accuracy and decreasing in size. This has made position sensors for use in tracking portions of an anatomical body during surgical procedures more feasible.
However, in order to accurately track areas of interest in an anatomical body, it is necessary to rigidly fix the position sensor near or at a location of interest in the anatomical body. It is also necessary to then register the position sensor with the anatomical body. A position sensor is registered to an anatomical body by correlating the position of the position sensor in the anatomical body to the determined position of the position sensor in the frame of reference. At that time, the location of interest in the anatomical body can be tracked in a fixed frame of reference, such as the operating room frame of reference, by determining the position of the position sensor.
A number of position sensors have been used in the past. Recently, magnetic sensor coils or fibre optic sensors that are reasonably small, and therefore can be substantially unobtrusively inserted into an anatomical body, have been successfully used.
However, the prior art suffers from the disadvantage that it is difficult to register the position sensors to the anatomical body. Methods for registering the position sensor in the anatomical body have included obtaining an image of the anatomical body after insertion of the position sensor and attempting to register the position sensor to the anatomical body from the acquired image. However, this suffers from the disadvantage that the position sensor is not always easily identifiable in the acquired image. Furthermore, while it may be possible to determine the position of the position sensor in the anatomical body, sufficient information may not be available from the image to determine and register both the position as well as orientation of the position sensor. Because of this, it may not be possible to determine all of the degrees of freedom, such as movement along the x, y, z axes, as well as three orientation coordinates, namely pitch, yaw and roll.
In some embodiments, it may be desirable that the position sensor be permitted to move relative to the anatomical body. However, in most cases, it is preferred that there be no relative movement between the position sensor and the location of interest in the anatomical body. Most prior art devices and methods for registering the position sensor in an anatomical body suffer from the disadvantage that there may be relative movement between the position sensor and the anatomical body. Accordingly, in addition to a method and device for accurately registering the position of the position sensor in an anatomical body, there is a need in the art for a device and method to reliably fix the position sensor to the anatomical body, thereby avoiding relative movement during the procedure. There is also a need in the art for reliable devices and methods to insert the position sensor into the anatomical body.